(1) Technical Field
The present invention relates to an image forming apparatus having a mechanism for applying an AC component and a DC component to a photoconductor by a contact or proximate electrification system using discharge as an electrifying principle to uniformly electrify the photoconductor, and particularly to a technique of measuring the film thickness of the photoconductor.
(2) Related Art
Various kinds of members (for example, an electrifying roller, a developing brush, a transfer roller, a cleaning brush, a cleaning blade, etc.) are disposed on the surface of a photoconductor mounted in an image forming apparatus while brought into physical contact with the surface of the photoconductor. Therefore, the photoconductive layer formed on the surface of the photoconductor repeats the physical contact with the above members every time an image forming operation is carried out, and thus the surface of the photoconductive layer wears gradually. Particularly, the rubbing force of the cleaning brush or the cleaning blade is strong, and it is a great factor causing abrasion of the photoconductive layer.
When the thickness of the photoconductive layer is reduced by some degree or more due to such abrasion, the photosensitivity is remarkably weakened or the electrification characteristic is degraded, so that it is impossible to uniformly electrify the surface to a desired potential or it is impossible to form a clear image. Therefore, it is required to measure the thickness of the photoconductive layer of the photoconductor and inform the lifetime of the photoconductor to users.